The present invention relates to an array of acoustical returner devices to reflect sound back in the incident direction. The acoustics of a room are controlled by the room's shape and volume, as well as reflections from surface treatments and the room's contents. Traditionally, sound absorbing and reflecting surfaces were used to control reflections. In 1984, co-Applicant Dr. Peter D'Antonio introduced the reflection phase grating into the pantheon of surface treatments. These surfaces were based on mathematical number theory sequences and numerical optimization and uniformly scattered the incident sound over a wide range of desirable frequencies for any angle of incidence. The present invention teaches a new addition to the toolbox of acoustical surface treatments. It is based on the tri-rectangular tetrahedron geometric shape and has the unique ability to return incident sound back in the direction of incidence, like a boomerang. A tetrahedron is a pyramid having four planar triangular faces. The tri-rectangular tetrahedron consists of three mutually perpendicular faces forming a corner.
Tri-rectangular tetrahedrons are generally known and are often referred to as corner reflectors. Such corner reflectors are known for use in reflecting light or electromagnetic radiation directly back to their source. The present invention contemplates using a tri-rectangular tetrahedron to reflect sound waves back to their source. Additionally, the present invention contemplates a filtering aspect that allows concentration of the reflected arrays solely to the bandwidth of the spoken word. This combination of aspects is not known in the prior art.